From tekma–(at)–xecpc.com Thu Oct 17 11:57:28 CDT 1996
Article: 16362 of rec.audio.tubes
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From: tekma–(at)–xecpc.com (Brendan Biever)
Newsgroups: rec.audio.tubes
Subject: Special Quality Valves: 12AX7
Date: 17 Oct 1996 05:46:39 GMT
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Some information for tubephiles………….
BRIMAR SPECIAL QUALITY TUBES
—————————-
The limiting factor in performance and reliability of valves (tubes)
lies in the tube pins and socket rather than in the tube itself.
Features of Brimar Flying Lead Special Quality Tubes:
* Ruggedised construction: Improved design of micas to eliminate
electrode movement, with control of mica and internal bulb dimensions
to precision limits. This eliminates rattle noise and microphony,
at the same time obviating cathode poisoning by gas evolution
resulting from frictional movement between mica and glass
* Redesign of grid profiles to control resonances arising from
vibration and shock
* Improved metal piece-parts giving greater mechanical rigidity
* Redesign of connecting links and stem wires to reduce the possibility
of failure
* Specially processed tungsten and advanced methods of heater coating
to give a greatly improved heater life
* Long life (10,000+ hours) Deterioration of electrical characteristics
over 10,000 hours of operation is less than 30%
LOW CATHODE INTERFACE IMPEDANCE:
The low Cathode interface impedance feature of Brimar Long-Life valves
is of considerable importance in many applications. In use, valves build
up a resistive layer between the metallic cathode and its emissive
coating. As this resistive layer appears in the cathode circuit, it
results in a negative feedback condition giving the valve a reduced
performance figure due to the loss of slope. The growth of this
interface impedance is more likely to occur where valves are used with
very low cathode current or in cut-off condition for long periods.
This also applies where valves are required to give high pulse
current after a long period of low current operation. To overcome this
problem Brimar Long-Life valve types incorporate new cathode alloys
which, as well as giving increased strength at working temperatures,
virtually eliminate cathode interface growth.
I have a few of the special quality flying lead CV4035=12AX7
and CV4069=12AU7.
Regards,
Brendan Biever
tekma–(at)–xecpc.com
(414) 208-0353 (phone/fax)
